Mounting structure for thermistor with positive resistance-to-temperature characteristic

Abstract

A thermistor with positive resistance-to-temperature characteristic used in a overcurrent protection circuit has electrodes on mutually opposite main surfaces and is mounted to a substrate having electrically conductive members such that deterioration of its voltage resistance due to heat emission can be controlled. A spacer with smaller thermal conductivity than the substrate and penetrated by a conductor piece with a small cross-sectional area is inserted between solder materials connecting to one of the thermistor electrodes. The other electrode is contacted by an elongated connecting member through its sectional surface transverse to its longitudinal direction such that the cross-sectional area of electrical conduction is reduced.

What is claimed is: 
     
       1. A structure comprising: a substrate having a mounting surface;   a conductive land formed on said mounting surface of said substrate;   a thermistor having a main surface;   an electrode on said main surface of said thermistor in a face-to-face relationship with and separated from said conductive land;   a non-metallic membrane covering a portion of said conductive land; and   a solder portion on an uncovered portion of said conductive land not covered by said non-metallic membrane, said electrode and said conductive land being electrically connected only through said solder portion, said non-metallic membrane serving to limit sectional area of said solder portion and to thereby limit heat conduction through said solder portion.   
     
     
       2. The structure of claim 1 wherein said thermistor has another electrode on an opposite surface to said main surface, said structure further comprising an electrically connecting member which electrically connects said another electrode on said thermistor to said substrate. 
     
     
       3. The structure of claim 2 wherein said non-metallic membrane comprises a glass glaze. 
     
     
       4. The structure of claim 1 wherein said non-metallic membrane comprises a glass glaze.